Vehicle manufacturers outfit their vehicles with an increasing number of wireless communications capabilities. Telematics units installed on modern vehicles can wirelessly communicate both voice and data transmissions between the vehicle and a variety of recipients, such as a central facility. Telematics units are usually registered with a cellular service that provides wireless communications services to users of those units. A telematics service provider may wirelessly communicate data between the central facility and a vehicle or vehicle telematics unit using the cellular service. However, the telematics service provider may send requests to communicate with vehicles that are unavailable to communicate for any one of a variety of reasons. To follow up unresponsive communication requests, telematics service providers often resort to sending additional requests. But these additional requests involve increased data costs which, in turn, increases the ultimate cost of communicating with a vehicle. And if the vehicle telematics unit is unable to communicate, the telematics service provider has no way of knowing this. In the meantime, the telematics service provider may continue to incur additional costs by needlessly attempting to communicate with a vehicle that is unable to respond.